This invention relates to an optical information recording medium, such as a magneto-optical disk, which is used for recording information by an irradition of a laser beam.
Various optical information recording media of the type are already known. For example, an optical information recording medium is disclosed by Sakuya Tamada and five others in Japanese Journal of Applied Physics, Vol. 28 (1989), Supplement 28-3, pp. 67-70, under the title of "Design Concept of Magneto-Optical Disk".
In the manner which will later be described more in detail, the recording medium comprises a substrate, a protective layer, a recording layer between the substrate and the protective layer, and a reflecting layer between the protective and the recording layers. The substrate is made of polycarbonate and therefore is transparent for the laser beam. The protective layer is made of an organic material. The reflecting layer contains aluminum (Al) and therefore is opaque for the laser beam.
As will later be described in detail, the recording medium has a recording density which is relatively high. Therefore, the recording medium enables an information recording system to have a large record capacity.
It is assumed that the reflecting layer is subjected to oxidation and deflection when the recording medium is used or preserved in an environment of a high temperature and humidity for a long time. Namely, the recording medium is disadvantageous in its weather resistance. This is because the protective layer of the organic material is insufficient to protect transmission of moisture.